Configuration validation in a mixed node topology

ABSTRACT

Techniques for validating configuration changes in a mixed node topology are provided. In one embodiment, a device can identify a link to be removed from a topology comprising a plurality of nodes, where the plurality of nodes includes one or more nodes of a first type and one or more nodes of a second type. The device can then determine whether the removal of the link from the topology would require data traffic between two nodes of the first type to pass through a node of the second type.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims the benefit and priority under 35 U.S.C.119(e) of U.S. Provisional Application No. 61/825,451, filed May 20,2013, entitled “FAILSAFE CONFIGURATION VERIFICATION IN A STACKINGSYSTEM,” the entire contents of which are incorporated herein byreference for all purposes.

BACKGROUND

As known in the art, a “stackable switch” is a network switch that canoperate independently as a standalone device or in concert with one ormore other stackable switches in a “stack” or “stacking system.” FIG. 1Aillustrates the front face of an exemplary stackable switch 100according to an embodiment. As shown, stackable switch 100 includes aset of data ports 102, a set of stacking ports 104, and a console port106. Data ports 102 are operable for connecting stackable switch 100 toone or more hosts and/or data networks. Stacking ports 104 are operablefor linking stackable switch 100 to other stackable switches in the samestacking system/topology. Stacking ports 104 can be dedicated ports(i.e., ports designed specifically for stacking) or high bandwidth datauplink ports that operate in a stacking mode. Finally, console port 106is operable for accessing the management console of stackable switch 100in order to perform various device management functions.

FIG. 1B illustrates an exemplary stacking system 150 according to anembodiment. As shown, stacking system 150 comprises a number ofstackable switches 152, 154, and 156 (each similar to stackable switch100 of FIG. 1A) that have been linked together via their respectivestacking ports. In the example of FIG. 1B, stackable switches 152, 154,and 156 form a ring topology. In addition, stackable switch 154 isdesignated as the “master” unit of stacking system 150, which means thatswitch 154 serves as the point of user contact for all managementfunctions of system 150. For instance, stackable switch 154 can acceptand process user commands directed to the overall configuration ofstacking system 150. Stackable switch 154 can also communicate withnon-master units 152 and 156 on an as-needed basis in order to propagatevarious types of management commands and data to those units.

Generally speaking, prior art stacking systems are limited to relativelysimple topologies like the ring topology depicted in FIG. 1B. However,new stacking technologies, such as Brocade Communications Systems'“HyperEdge” technology, support more complex topologies (e.g., arbitrarymeshes). These complex topologies are beneficial because they canprovide better performance (through reduced switch-to-switch latency)and superior resiliency (via redundant stacking paths). In addition,HyperEdge supports a feature known as “mixed” stacking, which allowshigh-end stackable switches (i.e., switches with more features, ports,and/or bandwidth) to be combined with low-end stackable switches (i.e.,switches with fewer features, ports, and/or bandwidth) in a singlestacking system. This mixing of high-end and low-end units can increasethe scalability and cost effectiveness of the system.

Unfortunately, while complex topology support and mixed stacking haveclear benefits for users, they can also complicate stacking systemadministration and management, particularly in instances where anadministrator wishes to make topology configuration changes. Forexample, consider stacking system 200 depicted in FIGS. 2A and 2B, whichcomprises three high-end switches 202, 204, 206 and three low-endswitches 208, 210, 212 that are interconnected via a mesh-like topology.High-end switch 202 is the master unit in this configuration. Assumethat an administrator attempts to remove the stacking link betweenhigh-end switch 206 and low-end switch 212 from the system's topologyconfiguration as shown in FIG. 2A. In this scenario, the removal of thestacking link will cause low-end switch 212 to be unreachable by themaster unit (i.e., high-end switch 202), and thus will break the system(since switch 202 can no longer communicate management commands/data toswitch 212).

As another example, assume that the administrator attempts to remove thestacking link between high-end switches 202 and 204 from the system'stopology configuration as shown in FIG. 2B. In this scenario, theremoval of the stacking link will force traffic between high-endswitches 202 and 204 to flow though low-end switches 208 and 210. This,in turn, can result in congestion and reduced system performance, sincelow-end switches will typically have less bandwidth capacity on theirstacking ports than high-end switches (e.g., 10 GB/port on low-endswitches vs. 40 GB/port on high-end switches).

SUMMARY

Techniques for validating configuration changes in a mixed node topologyare provided. In one embodiment, a device can identify a link to beremoved from a topology comprising a plurality of nodes, where theplurality of nodes includes one or more nodes of a first type and one ormore nodes of a second type. The device can then determine whether theremoval of the link from the topology would require data traffic betweentwo nodes of the first type to pass through a node of the second type.

The following detailed description and accompanying drawings provide abetter understanding of the nature and advantages of particularembodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A depicts a stackable switch according to an embodiment.

FIG. 1B depicts a stacking system according to an embodiment.

FIG. 2A depicts a scenario where the removal of a stacking link resultsin an unreachable unit.

FIG. 2B depicts a scenario where the removal of a stacking link causestraffic between two high-end units to flow through a low-end unit.

FIG. 3 depicts a mixed node topology according to an embodiment.

FIG. 4 depicts an algorithm for validating the removal of a link in amixed node topology according to an embodiment.

FIGS. 5A and 5B depict example applications of the algorithm of FIG. 3.

FIG. 6 depicts a network switch according to an embodiment.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousexamples and details are set forth in order to provide an understandingof various embodiments. It will be evident, however, to one skilled inthe art that certain embodiments can be practiced without some of thesedetails, or can be practiced with modifications or equivalents thereof.

The present disclosure describes techniques for automatically validatingconfiguration changes in a mixed node topology. As used herein, a “mixednode topology” refers to a set of interconnected nodes, where the setincludes at least two different node types, and where some of the nodetypes are more “capable” than others (e.g., may support greaterbandwidth, a larger number of ports, a higher level of securityclearance, etc.). In addition, the set of interconnected nodes includesa master node of the most capable node type. In one set of embodiments,a particular node in the topology (e.g., the master node) can identify alink to be removed from the topology. For example, the master node canreceive a user command to remove the link (or a port/trunk associatedwith the link). The master node can then execute a validation algorithmto ensure that the removal of the link will not cause (1) any node tobecome unreachable by the master node, and (2) traffic between two nodesto flow through a node that is less capable than either of the twonodes. If the algorithm returns a successful result (indicating that theremoval of the link will not cause (1) and/or (2)), the master node canallow the link removal to occur. On the other hand, if the algorithmreturns an unsuccessful result (indicating that the removal of the linkwill cause (1) or (2)), the master node can prevent the link from beingremoved from the topology.

In certain embodiments, the validation algorithm noted above can beparticularly useful when applied to stacking systems that use mixedstacking in combination with complex (e.g., mesh-like) topologies. Forexample, the algorithm can avoid the problematic scenarios describedwith respect to stacking system 200 of FIGS. 2A and 2B. However, itshould be appreciated that embodiments of the present invention are notlimited to stacking systems, and may be used to validate link removal inany arbitrary mixed node topology (e.g., general L2/L3 networks orfabrics).

FIG. 3 depicts an example of a mixed node topology (300) according to anembodiment. As shown, topology 300 includes a set of nodes of a firsttype (i.e., 302, 304, 306, 308, 310, 312) that are identified by a heavyoutline, and a set of nodes of a second type (i.e., 314, 316) that areidentified by a lighter outline. Node 302 is designated a master node,and thus is responsible for facilitating the configuration andmanagement of topology 300.

In the example of FIG. 3, the nodes of the first type are “high-end”nodes (e.g., high-end stackable switches), while the nodes of the secondtype are “low-end” nodes (e.g., low-end stackable switches).Accordingly, high-end nodes 302, 304, 306, 308, 310, 312 have moreand/or superior capabilities than low-end nodes 314, 316. For example,in a particular embodiment, high-end nodes 302, 304, 306, 308, 310, 312can have higher bandwidth communication ports than low-end nodes 314,316. This means that the links directly interconnecting the high-endnodes (i.e., 318, 320, 322, 324, 326, 328) can support a greater datathroughout than the links interconnecting the low-end nodes with eachother (or with the high-end nodes) (i.e., 330, 332, 334). In alternativeembodiments, high-end nodes 302, 304, 306, 308, 310, 312 can have othercharacteristics that distinguish these nodes from low-end nodes 314, 316(e.g., a larger number of ports, more advanced network processingcapabilities, a higher level of security clearance, etc.).

As discussed in the Background section, there are at least two potentialissues that may arise when removing links from a complex, mixed-nodetopology such as topology 300 of FIG. 3. First, the removal of a linkmay cause one or more nodes to be inadvertently “severed” from (i.e.,rendered unreachable by) master node 302, thereby preventing master node302 from communicating management commands and/or data to the severednodes. Second, the removal of a link may cause traffic between two ormore high-end nodes (e.g., 302, 304, 306, 308, 310, 312) to traversethrough a low-end node (e.g., 314, 316). Since, in the example of FIG.3, the links between high-end nodes and low-end nodes have a lowerbandwidth capacity than the links directly interconnecting high-endnodes, this situation can undesirably lead to congestion and reducedsystem performance.

To address these (and other similar) issues, in various embodimentsmaster node 302 can execute a validation algorithm at the time a linkremoval is to occur within topology 300 (e.g., at the time anadministrator or other agent submits a “remove link” or “remove port”command). In one embodiment, the validation algorithm can check whetherthe removal of the link will result in any unreachable nodes. In afurther embodiment, the validation algorithm can check whether theremoval of the link will cause traffic between any two nodes to flowthough a less capable node. If the algorithm determines that either ofthese scenarios will occur, master node 302 can block the link removalfrom proceeding. In this way, the undesirable consequences associatedwith these scenarios can be automatically avoided, without any manualintervention by a user or administrator.

It should be noted that this validation algorithm can be applied anyarbitrary topology (e.g., ring, linear, mesh, etc.), and is not limitedto specific types of topologies. Thus the same algorithm may be usedacross a variety of different deployments, each having differenttopological requirements/characteristics. In addition, although topology300 depicts only two node types for purposes of illustration (i.e., ahigh-end node type and low-end node type), the validation algorithm maybe applied to topologies that have more than two different node types(where each node type has a corresponding “capability” level). In theseembodiments, the algorithm can ensure that traffic between any two nodesin the topology (of the same or different node types) will not passthrough a node of a less capable type than either of the two nodes.

FIG. 4 depicts a flowchart 400 that can be performed by master node 302of FIG. 3 for carrying out the validation algorithm described aboveaccording to an embodiment. Flowchart 400 assumes that master node 302has access to the current configuration of topology 300.

At block 402, master node 302 can identify a link to be removed fromtopology 300. For example, in embodiments where topology 300 is astacking system, master node 302 can receive a user command to remove aparticular stacking port or trunk from a stackable switch in the system.Master node 302 can then identify the link to be removed based on thespecified port/trunk ID.

At block 404, master node 302 can create a copy of the current topologyconfiguration and remove the link from the copy. Master node 302 cansubsequently enter a loop for each endpoint of the link (block 406).

Within the loop of block 406, master node 302 can first create a “nodeset” and add the current endpoint node as the node set's initial member(block 408). Upon creating the node set, master node 302 can enter asecond loop for each node set member (block 410).

Within the second loop of block 410, master node 302 can, for each nodedirectly connected to the current node set member in the copy of thetopology configuration, add the node to the node set (block 412). If thenode is already part of the node set, it is not added again. In aparticular embodiment, as part of the processing of block 412, masternode 302 can enforce a restriction where a directly connected node isnot added to the node set if the directly connected node is less capablethan the current node set member (e.g., the directly connected node is alow-end node and the current node set member is a high-end node). In thecontext of topology 300 of FIG. 3, this restriction effectively preventsthe algorithm from considering paths through topology 300 that flow froma high-end node though a low-end node and back to a high-end node.

Once all of the directly connected nodes for the current node set memberhave been processed (and added to the node set if appropriate), masternode 302 can check whether the node set now includes itself (i.e., themaster node) (block 414). In other words, master node 302 can checkwhether a path has been established from the endpoint node to the masternode. If not, the current iteration of loop 410 can end (block 416) andmaster node 302 can repeat loop 410 in order to recursively processadditional members in the node set (including new members added at block412). If all of members in the node set are processed and the node setstill does not include the master node, master node 302 can concludethat there is no viable path from the endpoint node to the master nodeand can return a “FAIL” result (indicating that the link removal shouldnot be allowed) (block 418).

On the other hand, if the node set does include the master node at somepoint during loop 410, master node 302 can check whether the currentendpoint node (within loop 406) is the last (i.e., second) endpoint nodeto be processed. If so, master node 302 can conclude there are viablepaths between each endpoint node of the removed link and the masternode, and can return a “SUCCESS” result (indicating that the linkremoval should be allowed) (block 424). Otherwise, the current iterationof loop 406 can end (block 422) and master node 302 can repeat loop 406in order to process the second endpoint node of the removed link. Thissecond iteration of loop 406 will ultimately result in a “FAIL” resultper block 418 or a “SUCCESS” result per block 424.

It should be appreciated that the validation algorithm of FIG. 4 isillustrative and various modifications are possible. For example, afteridentifying the link to be removed at block 402, in certain embodimentsmaster node 302 can first check whether the link is “live” (i.e.,physically connected). Master node 302 can determine this by, e.g.,referencing an internal representation of the physical topology, orrunning a topology discovery algorithm. If the link is not live, masternode 302 can return a “SUCCESS” result (i.e., allow the link removal toproceed), without continuing with the rest of the algorithm.

In further embodiments, rather than being performed solely by masternode 302, portions of flowchart 400 can be performed by other nodes ordevices in topology 300. For instance, in a particular embodiment, eachendpoint node of the removed link can perform a slightly modifiedversion of blocks 408-424 that returns either a “SUCCESS” result (if themaster node is added to the node set for the endpoint node) or a “FAIL”result (if the master node is never added to the node set for theendpoint node). Each endpoint node can then transmit its result tomaster node 302, which can allow the link removal if both endpoint nodesreturn “SUCCESS” or block the link removal if either endpoint nodereturns “FAIL.” One of ordinary skill in the art will recognize manyvariations, modifications, and alternatives.

To further clarify the operation of the validation algorithm of FIG. 4,FIGS. 5A and 5B depict exemplary scenarios 500 and 550 where thealgorithm is used to validate the removal of certain links in topology300 of FIG. 3. For instance, in FIG. 5A, the link to be removed is link326 (between high-end nodes 306 and 310). In this scenario, thealgorithm first processes endpoint node 306 and a node set is createdthat includes node 306 as its initial member (per block 408 of FIG. 4).The algorithm then runs through loop 410, and the node set for endpointnode 306 grows to {306, 304, 308} in the first iteration, and {306, 304,308, 302} in the second iteration.

Since node 302 is the master node, the algorithm determines that itsprocessing can continue (per blocks 414 and 420), and moves on tocreating a node set for second endpoint node 310 (that includes node 310as its initial member). The algorithm then runs through loop 410 forendpoint node 310, and the node set for endpoint node 310 grows to {310,312} in the first iteration (note that directly connected node 316 isnot added to the node set since node 310 is a high-end node and node 316is a low-end node). At this point, there are no further nodes in thenode set to be processed, and the node set does not include master node302. Accordingly, the algorithm concludes that there is no viable pathbetween endpoint node 310 and master node 302 and returns a “FAIL”result (thereby blocking the removal of link 326).

Turning now to FIG. 5B, the link to be removed in this scenario is link332 (between low-end nodes 314 and 316). Here, the algorithm firstprocesses endpoint node 314 and a node set is created that includes node314 as its initial member (per block 408). The algorithm then runsthrough loop 410, and the node set for endpoint node 314 grows to {314,308} in the first iteration, and {314, 308, 306, 302} in the seconditeration.

Since node 302 is the master node, the algorithm determines that itsprocessing can continue (per blocks 414 and 420), and moves on tocreating a node set for second endpoint node 316 (that includes node 316as its initial member). The algorithm then runs through loop 410 forendpoint node 316, and the node set for endpoint node 316 grows to {316,310} in the first iteration, {316, 310, 306, 312} in the seconditeration, {316, 310, 306, 312, 304, 308} in the third iteration, and{316, 310, 306, 312, 304, 308, 302} in the fourth iteration. Since node302 is the master node and all endpoint nodes are now processed, thealgorithm concludes that there are viable paths between each endpointnode 310, 316 and master node 302 and returns a “SUCCESS” result(thereby allowing the removal of link 332).

FIG. 6 depicts a network switch 600 according to an embodiment. Networkswitch 600 can be used to implement any of the nodes/stackable switchesdescribed in the foregoing disclosure, such as stackable switch 100 ofFIG. 1A.

As shown, network switch 600 includes a management module 602, a switchfabric module 604, and a number of I/O modules 606(1)-606(N). Managementmodule 602 represents the control plane of network switch 600 and thusincludes one or more management CPUs 608 for managing/controlling theoperation of the device. Each management CPU 608 can be a generalpurpose processor, such as a PowerPC, Intel, AMD, or ARM-basedprocessor, that operates under the control of software stored in anassociated memory (not shown).

Switch fabric module 604 and I/O modules 606(1)-606(N) collectivelyrepresent the data, or forwarding, plane of network switch 600. Switchfabric module 604 is configured to interconnect the various othermodules of network switch 600. Each I/O module 606(1)-606(N) can includeone or more input/output ports 610(1)-610(N) that are used by networkswitch 600 to send and receive data packets. As noted with respect toFIGS. 1A and 1B, ports 610(1)-610(N) can comprise data ports forcommunicating with hosts/other network devices, as well as stackingports for communicating with other switch units in the same stackingsystem. Each I/O module 606(1)-606(N) can also include a packetprocessor 612(1)-612(N). Packet processor 612(1)-612(N) is a hardwareprocessing component (e.g., an FPGA or ASIC) that can make wire speeddecisions on how to handle incoming or outgoing data packets.

It should be appreciated that network switch 600 is illustrative and notintended to limit embodiments of the present invention. Many otherconfigurations having more or fewer components than switch 600 arepossible.

The above description illustrates various embodiments of the presentinvention along with examples of how aspects of the present inventionmay be implemented. The above examples and embodiments should not bedeemed to be the only embodiments, and are presented to illustrate theflexibility and advantages of the present invention as defined by thefollowing claims. For example, although certain embodiments have beendescribed with respect to particular process flows and steps, it shouldbe apparent to those skilled in the art that the scope of the presentinvention is not strictly limited to the described flows and steps.Steps described as sequential may be executed in parallel, order ofsteps may be varied, and steps may be modified, combined, added, oromitted. As another example, although certain embodiments have beendescribed using a particular combination of hardware and software, itshould be recognized that other combinations of hardware and softwareare possible, and that specific operations described as beingimplemented in software can also be implemented in hardware and viceversa.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense. Other arrangements,embodiments, implementations and equivalents will be evident to thoseskilled in the art and may be employed without departing from the spiritand scope of the invention as set forth in the following claims.

What is claimed is:
 1. A method comprising: identifying, by a device, alink to be removed from a topology comprising a plurality of nodes, theplurality of nodes including one or more nodes of a first type and oneor more nodes of a second type; and determining, by the device, whetherremoval of the link from the topology would cause one or more nodes inthe plurality of nodes to become unreachable by a master node of thefirst type, wherein the determining comprises: removing the link from arepresentation of the topology; and for each endpoint node located at anendpoint of the link: creating a node set that includes the endpointnode; adding, to the node set, other nodes in the plurality of nodesthat are directly linked to the endpoint node in the representation ofthe topology; and subsequently to the adding, checking whether the nodeset includes the master node.
 2. The method of claim 1 wherein thetopology is a mesh topology.
 3. The method of claim 1 wherein the one ormore nodes of the first type are more capable than the one or more nodesof the second type.
 4. The method of claim 3 wherein the one or morenodes of the first type support greater port bandwidth, a larger numberof ports, or a higher level of security clearance than the one or morenodes of the second type.
 5. The method of claim 1 further comprising:determining whether removal of the link from the topology would requiredata traffic between two nodes of the first type to pass through a nodeof the second type.
 6. The method of claim 1 wherein if the endpointnode is of the second type, the adding comprises adding directly linkednodes that are of the first type or the second type, and wherein if theendpoint node is of the first type, the adding comprises adding directlylinked nodes that are of the first type, without adding any directlylinked nodes that are of the second type.
 7. The method of claim 6wherein the determining further comprises: if the node set does notinclude the master node, repeating the adding and the checking foradditional nodes in the node set; else if the node set includes themaster node, returning a first result.
 8. The method of claim 7 whereinthe determining further comprises: if every node in the node set hasbeen processed and the first result has not been returned, returning asecond result.
 9. The method of claim 8 further comprising: preventingremoval of the link if the second result is returned for any endpointnode of the link.
 10. The method of claim 1 wherein the device is themaster node.
 11. The method of claim 1 wherein the topology represents astacking system, and wherein each node in the plurality of nodescorresponds to a stackable switch in the stacking system.
 12. The methodof claim 11 wherein the identifying comprises: receiving a user commandspecifying a stacking port or a stacking trunk of a node in theplurality of nodes; and identifying the link based on the stacking portor the stacking trunk.
 13. A non-transitory computer readable mediumhaving stored thereon program code executable by a processor, theprogram code comprising: code that causes the processor to identify alink to be removed from a topology comprising a plurality of nodes, theplurality of nodes including one or more nodes of a first type and oneor more nodes of a second type; and code that causes the processor todetermine whether removal of the link from the topology would cause oneor more nodes in the plurality of nodes to become unreachable by amaster node of the first type, wherein the determining comprises:removing the link from a representation of the topology; and for eachendpoint node located at an endpoint of the link: creating a node setthat includes the endpoint node; adding, to the node set, other nodes inthe plurality of nodes that are directly linked to the endpoint node inthe representation of the topology; and subsequently to the adding,checking whether the node set includes the master node.
 14. Thenon-transitory computer readable medium of claim 13 wherein the topologyis a mesh topology.
 15. The non-transitory computer readable medium ofclaim 13 wherein the one or more nodes of the first type are morecapable than the one or more nodes of the second type.
 16. Thenon-transitory computer readable medium of claim 13 wherein the programcode further comprises: program code that causes the processor todetermine whether removal of the link from the topology would requiredata traffic between two nodes of the first type to pass through a nodeof the second type.
 17. A network device comprising: a processor; and anon-transitory computer readable medium having stored thereon programcode which, when executed by the processor, causes the processor to:identify a link to be removed from a topology comprising a plurality ofnodes, the plurality of nodes including one or more nodes of a firsttype and one or more nodes of a second type; and determine whetherremoval of the link from the topology would cause one or more nodes inthe plurality of nodes to become unreachable by a master node of thefirst type, wherein the determining comprises: removing the link from arepresentation of the topology; and for each endpoint node located at anendpoint of the link: creating a node set that includes the endpointnode; adding, to the node set, other nodes in the plurality of nodesthat are directly linked to the endpoint node in the representation ofthe topology; and subsequently to the adding, checking whether the nodeset includes the master node.
 18. The network device of claim 17 whereinthe topology is a mesh topology.
 19. The network device of claim 17wherein the one or more nodes of the first type are more capable thanthe one or more nodes of the second type.
 20. The network device ofclaim 17 wherein the program code further causes the processor todetermine whether removal of the link from the topology would requiredata traffic between two nodes of the first type to pass through a nodeof the second type.